Forss N, Jousmäki V, Hari R
Low Temperature Laboratory, Helsinki University of Technology, Otakaari 3A, Espoo, Finland.
Brain Res. 1995 Jul 10;685(1-2):68-76. doi: 10.1016/0006-8993(95)00424-o.
We recorded somatosensory evoked magnetic fields from eight healthy subjects with a 122-channel whole-scalp SQUID magnetometer. The stimulus sequence consisted of 'standard' stimuli (85%) delivered to palmar side of the left thumb with an interstimulus interval of 0.6 s and of 'deviants' (15%), randomly interspersed among the standards, to little finger, and vice versa. Both stimuli activated four source areas: the contralateral primary somatosensory cortex (SI), the contra-and ipsilateral secondary somatosensory cortices (SII), and the contralateral posterior parietal cortex (PPC). The short-latency (20-40 ms) responses originated in the SI cortex, whereas long-latency responses arose from all 4 areas. At SII and PPC, the deviant stimuli elicited larger responses when presented alone, without intervening standards, than among standards. This implies interaction between afferent impulses from the two fingers and/or partly intermingled cortical representations. Our findings show, in agreement with animal data, different excitatory/inhibitory balance in the various somatosensory areas.
我们使用一台122通道全头型超导量子干涉仪磁力计，记录了8名健康受试者的体感诱发磁场。刺激序列包括“标准”刺激（85%），以0.6秒的刺激间隔施加于左手拇指掌侧，以及“偏差”刺激（15%），随机穿插在标准刺激中，施加于小指，反之亦然。两种刺激均激活了四个源区域：对侧初级体感皮层（SI）、对侧和同侧次级体感皮层（SII）以及对侧后顶叶皮层（PPC）。短潜伏期（20 - 40毫秒）反应起源于SI皮层，而长潜伏期反应则来自所有四个区域。在SII和PPC区域，当单独呈现偏差刺激而无中间标准刺激时，引发的反应比在标准刺激中更大。这意味着来自两个手指的传入冲动之间存在相互作用和/或部分混合的皮层表征。我们的研究结果表明，与动物数据一致，不同体感区域存在不同的兴奋/抑制平衡。
